**2. The two-phase olive oil manufacturing process**

The failure to develop a suitable and economical effluent wastewater treatment technology for OMW has lead manufacturers of technology to develop the "ecological" two-phase process, which delivers oil as the liquid phase and a very wet olive cake (**two-phase olive mill solid waste -OMSW-**) as the solid residue. This technology has attracted special interest where water supplies are restricted and/or aqueous effluent must be reduced (Borja et al., 2006).

In the two-phase process a horizontally mounted centrifuge is used for primary separation of the olive oil fraction from the vegetable solid material and vegetation water. The resultant olive oil is further washed to remove residual impurities before finally being separated from this wash water in a vertical centrifuge. Therefore, the two-phase olive mills produce three identifiable and separate waste streams. These are:


Spain was the first country where the two-phase system was used and from there this new technology was installed around the world. The two-phase decanting reduces the water requirements. Nevertheless it has created a new solid residue, two-phase OMSW, which requires further investigation to find out how it must be handled.

The two-phase olive oil extraction process has several advantages over the three-phase centrifugation process (Alba et al., 2001; Di Giovacchino et al., 2001 and 2002):


m3/year) before the implantation of the two-phase extraction process in most of the Spanish olive oil factories, which represented an equivalent pollution of 10-16x106 inhabitants in the

The efforts to find a solution to the OMW problem are more than 50 years old (Borja et al., 2006). There are many different types of processes that have been tested: detoxification processes (such as physical, thermal, physicochemical, biological and combination of processes), recyclying and recovery of valuable components, production system modification, etc. However, none of the detoxification techniques on an individual basis allow the problem of disposal of OMW to be solved to a complete and exhaustive extent, effectively and in an ecologically satisfactory way. At the present state of OMW treatment technology, industry has shown little interest in supporting any traditional process (physical, chemical, thermal or biological) on a wide scale. This is because of the high investment and operational costs, the short duration of the production period (3-5 months)

The failure to develop a suitable and economical effluent wastewater treatment technology for OMW has lead manufacturers of technology to develop the "ecological" two-phase process, which delivers oil as the liquid phase and a very wet olive cake (**two-phase olive mill solid waste -OMSW-**) as the solid residue. This technology has attracted special interest where water supplies are restricted and/or aqueous effluent must be reduced (Borja et al., 2006).

In the two-phase process a horizontally mounted centrifuge is used for primary separation of the olive oil fraction from the vegetable solid material and vegetation water. The resultant olive oil is further washed to remove residual impurities before finally being separated from this wash water in a vertical centrifuge. Therefore, the two-phase olive mills produce three

2. The aqueous solid residues generated during the primary centrifugation (two-phase

3. The wash waters from the secondary centrifuge generated during the washing and

Spain was the first country where the two-phase system was used and from there this new technology was installed around the world. The two-phase decanting reduces the water requirements. Nevertheless it has created a new solid residue, two-phase OMSW, which

The two-phase olive oil extraction process has several advantages over the three-phase

The construction of the two-phase scroll centrifuge is less complicated and thus is more

 During operation of the three-phase scroll centrifuge the separated oil and water may be remixed; volatile compounds from the vegetation water may cause a sticky deposit

short milling period (Nioaunakis and Halvadakis, 2004).

and the small size of the olive mills (Borja et al., 2006).

identifiable and separate waste streams. These are:

purification of virgin olive oil.

OMSW).

on the centrifuge.

1. The wash waters generated during the initial cleansing of the fruit.

requires further investigation to find out how it must be handled.

centrifugation process (Alba et al., 2001; Di Giovacchino et al., 2001 and 2002):

reliable in operation and less expensive than the three-phase decanter.

**2. The two-phase olive oil manufacturing process** 


In addition, the disadvantages of two-phase manufacturing process are:

